The present invention relates generally to medical devices and methods and more particularly to devices and methods having utility in clinical applications for fat transfer.
Fat transfer, alternately termed fat grafting, comprises two or more procedures or sub-processes performed in series. Fat transfer processes are typically initiated with a fat harvesting procedure and are concluded with a fat re-injection procedure. The fat harvesting procedure and fat re-injection procedure are commonly performed on the same patient. In such cases, the fat transfer process is termed an autologous process.
Fat harvesting entails removing a harvested fat emulsion from the hypodermis of a patient. The hypodermis is the subdermal or subcutaneous innermost layer of the skin which is one of the primary sites on the body where fat is produced and stored. The harvested fat emulsion is characterized at least in part as native adipose material which appears as an amalgam of loose connective tissue and fat lobules. On a microscopic level, the native adipose material is characterized as an adipose tissue complex which is a diverse heterogeneous mixture including inter alia adipocytes, precursor adipocytes, stromal cells, stem cells, macrophages, free lipids dissociated from ruptured adipocytes, perivascular matrix, extracellular matrix and native scaffolding. Preferred harvesting sites on the body include the fatty lower layer of skin on the thighs or stomach of the patient. Fat harvesting is performed in accordance with any number of well-known techniques including liposuction or lipoplasty.
Fat re-injection entails injecting a re-injection material into an injection site that is different from the harvesting site. In the case of an autologous fat transfer process, the injection site is on the same body as the harvesting site, but is at a different location on the patient's body. The re-injection material is generally characterized as a fat-containing material. The preferred location of the injection site on the body depends on the particular clinical application for the fat transfer process. For example, potential injection sites in cosmetic applications for fat transfer include the skin of the face, breasts, cheeks, lips, buttocks, and/or chin. The re-injection material acts as a superficial filler in cosmetic applications to desirably increase volume at the injection site and enhance the appearance of the patient. Alternate injection sites may be selected for other clinical fat transfer applications, such as for skin anti-aging, hair regeneration, restoration of sun/radiation damaged skin, restoration of abnormally scarred skin, healing of chronic flesh wounds and treatment of many musculoskeletal disorders.
There are a number of intervening procedures that may be performed after the fat harvesting procedure and before the fat re-injection procedure, which are termed fat conditioning procedures. Fat conditioning procedures are designed to enhance the suitability of the re-injection material for use in the fat re-injection procedure. Many fat conditioning procedures are performed in serial combination with other fat conditioning procedures. One general type of fat conditioning procedure is termed fat decontamination. Fat decontamination procedures are designed in general to remove undesirable non-fat materials, termed contaminants, from the harvested fat emulsion before fat re-injection. Common contaminants in the harvested fat emulsion include such non-fat liquids as blood and tumescent fluid which are desirably excluded from the ultimate re-injection material.
A specific type of fat decontamination procedure is termed fat washing. Fat washing procedures are preferably performed on the harvested fat emulsion before any other intervening fat conditioning procedures and are frequently performed immediately after the harvested fat emulsion has been withdrawn from the body via the fat harvesting procedure. The fat washing procedure is initiated by fully mixing a volume of an aqueous washing liquid with the harvested fat emulsion. The resulting mixture of the harvested fat emulsion and aqueous washing liquid stratifies relatively rapidly into at least two layers. One layer is termed a contaminant-rich layer and another layer is termed a contaminant-lean layer. The contaminant-rich layer is characterized as having a significantly higher concentration of contaminants and aqueous washing liquid and a significantly lower concentration of fat than the contaminant-lean layer, whereas the contaminant-lean layer is characterized as having a significantly higher concentration of fat and a significantly lower concentration of contaminants and aqueous washing liquid than the contaminant-rich layer. The contaminant-lean and contaminant-rich layers are readily separable from one another by gravity. The resulting contaminant-lean layer, which is isolated from the contaminant-rich layer, is suitable for further fat conditioning before fat re-injection or may be suitable as is for use as the re-injection material in a fat re-injection procedure.
Another fat conditioning procedure is termed fat compounding. Fat compounding procedures enhance the composition of the re-injection material via the addition of certain desirable non-fat liquids, such as platelet rich plasma (PRP), to the re-injection material recovered from the harvested fat emulsion. Yet another common fat conditioning procedure is termed fat sizing. A harvested fat emulsion by its nature contains fat particles in a broad range of particle sizes upon its removal from the body. These fat particles may be classified in different particle size categories listed as follows from largest to smallest: macrofat, microfat, millifat and nanofat. The object of fat sizing procedures is to increase the fraction of nanofat in the re-injection material used in the ultimate fat re-injection procedure. An exemplary fat re-injection procedure using a re-injection material having a high concentration of nanofat is described in “Nanofat Grafting: Basic Research and Clinical Applications,” Tonnard, Patrick, et al., Plastic and Reconstructive Surgery Journal, v. 132(4), at pp. 1017-26, October 2013, which is incorporated herein by reference.
Nanofat is particularly suited for re-injection because it readily flows through very sharp, fine cannulas having a size range of about 27 to 30 gauge. Practitioners prefer to use these fine cannulas in fat re-injection procedures because they are less invasive and disruptive to the patient and can substantially reduce pain, bruising and/or other undesirable side effects of the fat re-injection procedure while simultaneously shortening patient recovery time. Fine cannulas also advantageously enable more precise placement of the re-injection material in the injection site, particularly with respect to intradermal and small joint placements, which are very challenging therapeutic sites. Nanofat advantageously does not substantially clog or otherwise impede flow through fine cannulas as compared to larger fat particle sizes which frequently clog them.
It is also believed that there may be substantial therapeutic advantages attributable to the use of nanofat versus larger fat particle sizes, particularly with respect to certain specific clinical fat transfer applications. For example, nanofat has been found to enhance the therapeutic efficacy of cosmetic applications for fat transfer by producing markedly better results in the ultimate appearance of the patient, particularly in the treatment of superficial dermal layers such as eyelids and the like, when compared to patients treated with larger particle-size fats. The reason for these therapeutic advantages is not fully understood, but it is believed that the therapeutic advantages result from factors in addition to, or other than, the small particle size of the nanofat. One theory is that there is a substantially greater residual presence of therapeutically beneficial adipose and non-adipose materials, some or all of which may be bioactive, that are coincidentally retained in the nanofat when it is isolated from the remainder of the harvested fat emulsion in preparation for re-injection and that the presence of these materials enhances the efficacy of the clinical fat transfer application. This theory is discussed in “Understanding Mechanical Emulsification (Nanofat) Versus Enzymatic Isolation of Tissue Stromal Vascular Fraction (tSVF) Cells from Adipose Tissue: Potential Uses in Biocellular Regenerative Medicine,” Alexander M. D., Robert W., Journal of Prolotherapy, v. 8:2016, at pp. e947-e960, Mar. 11, 2016, which is incorporated herein by reference. The adipose-derived tissue stromal vascular fraction of cells (AD-tSVF) is a highly desirable fraction of the adipose tissue complex for re-injection because it includes stromal cells and bioactive scaffolding.
Given the above-recited advantages attributable to the use of nanofat in fat re-injection procedures, fat sizing procedures that separate and recover the nanofat from the bulk harvested fat emulsion obtained in fat harvesting procedures are highly desirable. The recovered nanofat is the primary component of the re-injection material in the fat re-injection procedure, while the remainder of the harvested fat emulsion is excluded from the re-injection material or at least reduced in amount. Fat sizing procedures also desirably increase the volume and/or density of the nanofat in the ultimate re-injection material by breaking down the particle size of the fat in the harvested fat emulsion.
Additional fat conditioning procedures include centrifugation, filtration and decantation. In known centrifugation procedures, the harvested fat emulsion is rotated in a centrifuge container at high speed. The centrifugal force that the centrifuge applies to the harvested fat emulsion typically stratifies it into three discrete vertical layers of different density. The bottom centrifugation layer contains the most dense material, termed the pellet, and settles to the bottom of the centrifuge container. The top centrifugation layer contains the least dense material and rises to the top of the centrifuge container. The middle centrifugation layer contains an intermediate density material and resides between the top and bottom centrifugation layers in the centrifuge container. The majority of the nanofat has been found to reside in the middle centrifugation layer which the practitioner recovers as the re-injection material for re-injection into the body to the exclusion of the other centrifugation layers. An example of a specific centrifugation procedure is disclosed in our co-pending U.S. patent application Ser. No. 15/154,890 filed on May 13, 2016 and incorporated herein by reference.
In known filtration procedures, the harvested fat emulsion is applied to a filtration medium which permits nanofat to pass through it in the filtrate while trapping the unwanted remainder of the harvested fat emulsion on the filtration medium as a filter cake. An example of a specific filtration procedure is disclosed in our co-pending U.S. patent application Ser. No. 15/154,885 filed on May 13, 2016 and incorporated herein by reference.
In known decantation procedures, gravity acts on the harvested fat emulsion while it rests in a decanter for an extended period of time, e.g., several minutes or more. The force of gravity, like centrifugal force, causes the harvested fat emulsion to separate into multiple discrete layers of different density. The practitioner retrieves the nanofat layer, i.e., the layer containing the majority of the nanofat, as the re-injection material for re-injection into the body to the exclusion of the other layer(s) by simply pouring off each layer into separate containers.
A need is recognized herein for a fat conditioning apparatus having utility in any one of a plurality of procedures that efficiently and effectively produce a satisfactory re-injection material from a harvested fat emulsion for re-injection into the body of a patient. Accordingly, it is an object of the present invention to provide an apparatus that satisfies the above need. It is further an object of the present invention to provide one or more methods that satisfy the above need. These objects and others are accomplished in accordance with the invention described hereafter.